html {
  font-size: 15px;
}
body {
  width: 100vw;
  height: 100vh;
  display: grid;
  justify-content: center;
  align-content: center;
  background-color: #2c3e50;
}

article {
  width: 400px;
  height: 400px;
  border: solid 1px #ddd;
  position: relative;
  div {
    width: 100px;
    height: 100px;
    background: #000;
    transition-duration: 1s;
    transform-origin: center;
    transform: translate(-50%, -50%);
    position: absolute;
    left: 50%;
    top: 50%;
  }
  &:hover {
    & > div {
      transform: translate(-50%, -50%) rotate(360deg);
    }
  }
}
